1. Field of the Invention
The invention relates to a fuel cell, a method and apparatus of manufacturing the fuel cell.
2. Description of the Related Art
Japanese Patent Application Publication No. JP-A-2002-35985 discloses a fuel cell stack. This fuel cell stack has an elastic member provided at one end thereof to compensate for changes in tightening load. In particular, the gradual loosening or reduction in tightening force, caused by, for example, thermal expansion and contraction, or creep in the lengthwise direction of the stack. The elastic member may be a disc spring, for example, which is able to compensate for changes in the tightening load by adjusting to changes in the lengthwise direction of the fuel cell stack that are within the effective stroke range of the disc spring.
When a tightening load is applied to the fuel cell stack over an extended period of time, however, creep of an adhesive layer between separators of the cell module or the like causes the fuel cell stack to contract in the direction in which the cell modules are stacked. If a carbon separator is used, creep of the binder resin of the separator itself may occur. If the extent of contraction exceeds the amount of fluctuation in tightening load that can be compensated for by the disc spring, it will not be possible to prevent further loosening or decrease in tightening force.